1. Field of the Invention
The present invention relates generally to an apparatus and method for pathogen concentration reduction in and dehydration of sludge derived from a waste water or sewage treatment process, and more specifically to a means and method for significantly reducing the water, bacterial and viral content of such sludge at a relatively low temperature in a rapid, inexpensive manner adaptable to a wide variety of existing treatment facilities and capable of accommodating relatively high sludge volumes on a continuous basis.
2. State of the Art
Technology for, and adaptable to, drying moisture-containing waste and other materials of various origins has been in existence in many forms for almost a century. Examples of many prior art drying devices appear in U.S. Pat. Nos. 545,121; 572,258; 581,686; 1,099,330; 1,321,332; 1,459,302; 1,469,294; 2,151,320; 2,699,620; 2,862,462; 2,864,672; 3,716,002; 4,339,999; 4,639,217; and 4,970,803.
All of the prior art devices as exemplified in the above-referenced patents possess substantial deficiencies in their applicability to sludge drying. For example, the majority require installation of a substantial number of permanent foundation and structural support components on site, in addition to the actual operating components. The simpler prior art devices are not suited for receiving sludge on a continuous basis, and are quite limited in their batch capacity. All of the prior art devices require a fabrication or purchase of complex, relatively expensive components. Moreover, the sheer spatial volume of some of the prior art devices, and the multi-element nature of others renders them difficult, if not impossible, to install at existing waste treatment facilities where space is at a premium. Finally, most existing devices operate at very high, furnace-like temperatures which incinerate, rather than just dry, the material under treatment. Such an approach, in addition to requiring massive and costly energy input, can generate significant air pollution, both in the form of particulates and of toxic gases. Under current government environmental regulations, the gaseous output of the high temperature prior art devices requires costly scrubbing apparatus and other air pollution control devices to meet air quality standards. The air pollution problem is aggravated if the waste to be treated, as is many times the case with sludge, contains heavy metals and/or other toxins which are readily vaporized at high temperatures.
In recent years, more stringent government regulation of waste disposal procedures and the resulting need to minimize the sludge volume to ultimately be disposed of has resulted in a need for a sludge drying apparatus which is relatively simple in construction, straightforward in operation and easy to install at a variety of sites, both new and existing, of various diverse configurations. Very recently implemented legislation requiring pathogen concentration reduction in waste water or sewage sludge prior to application to the land or other ultimate disposition has compounded the problem of sludge treatment, and the prior art technology fails to provide the necessary solutions for high sludge volumes and at a relatively low cost.